The wife of a $1 million Chicago lottery winner who died of cyanide poisoning told ABC News that she was shocked to learn the true cause of his death and is cooperating with an ongoing homicide investigation.

"I want the truth to come out in the investigation, the sooner the better," said Shabana Ansari, 32, the wife of Urooj Khan, 46. "Who could be that person who hurt him?

"It has been an incredibly hard time," she said. "We went from being the happiest the day we got the check. It was the best sleep I've had. And then the next day, everything was gone."

Ansari, Khan's second wife, told the Chicago Sun-Times that she prepared what would be her husband's last meal the night before Khan died unexpectedly on July 20. It was a traditional beef-curry dinner attended by the married couple and their family, including Khan's 17-year-old daughter from a previous marriage, Jasmeen, and Ansari's father. Not feeling well, Khan retired early, Ansari told the paper, falling asleep in a chair, waking up in agony, then collapsing in the middle of the night. She called 911.

Khan, an immigrant from India who owned three dry-cleaning businesses in Chicago, won $1 million in a scratch-off Illinois Lottery game in June and said he planned to use the money to pay off his bills and mortgage, and make a contribution to St. Jude Children's Research Center.

"Him winning the lottery was just his luck," Ansari told ABC News. "He had already worked hard to be a millionaire before it."

Jimmy Goreel, who worked at the 7-Eleven store where Khan bought the winning ticket, described him to The Associated Press as a "regular customer ... very friendly, good sense of humor, working type of guy."

Khan's unexpected death the month after his lottery win raised the suspicions of the Cook County medical examiner. There were no signs of foul play or trauma so the death initially was attributed to arteriosclerotic cardiovascular disease, which covers heart attacks, stroke or ruptured aneurysms. The medical examiner based the conclusion on an external exam -- not an autopsy -- and toxicology reports that indicated no presence of drugs or carbon monoxide.

Khan was buried at Rosehill Cemetery in Chicago.

However, several days after a death certificate was issued, a family member requested that the medical examiner's office look further into Khan's death, Cook County Medical Examiner Stephen Cina said. The office did so by retesting fluid samples that had been taken from Khan's body, including tests for cyanide and strychnine.

When the final toxicology results came back in late November, they showed a lethal level of cyanide, which led to the homicide investigation, Cina said. His office planned to exhume Khan's body within the next two weeks as part of the investigation.

The Chicago Police Department said it has been working closely with the medical examiner's office. The police have not said whether or not they believe Khan's lottery winnings played a part in the homicide.

Khan had elected to receive the lump sum payout of $425,000, Ansari told the AP, adding that the winnings now are tied up as a probate matter.

Authorities also have not revealed the identity of the relative who suggested the deeper look into Khan's death. Ansari said it was not her, though she told the AP she has subsequently spoken with investigators.

"This is been a shock for me," she told ABC News. "This has been an utter shock for me, and my husband was such a goodhearted person who would do anything for anyone. Who would do something like this to him?

"We were married 12 years, [and] he treated me like a princess," she said. "He showered his love on me and now it's gone."